Congenital Mesoblastic Nephroma Mimic Wilms Tumor on 18 F-FDG PET/CT and PET/MR

ABSTRACT

Congenital mesoblastic nephroma is an extremely rare, low-grade malignant renal tumor in children. A 10-month-old boy and a 4-month-old girl were admitted to our hospital with a huge abdominal mass. For staging of the mass, 18 F-FDG PET/CT and PET/MR were performed showing a huge heterogeneous abdominal mass accompanied by extensive heterogeneous aggregation. Both of them were highly suspected to be Wilms tumor, the most common renal malignant tumor in children. However, histopathological examination after surgery confirmed congenital mesodermal nephroma.

Management of mixed type congenital mesoblastic nephroma: Case series and review of the literature

Congenital mesoblastic nephroma (CMN) is the most common renal tumor of infancy; however, it occurs infrequently with an incidence of 1 : 125,000. The cellular and classical variants are the most common subtypes of tumors, with a mixed variant occurring infrequently. We describe two cases of mixed variant CMN, which presented within days of each other differing in their clinical behavior. The first case followed a typical course, previously described in the literature, while the other deviated significantly. Traditionally, CMN presents as large abdominal mass in the neonatal period associated with a paraneoplastic syndrome, which can result in hypertension or hypercalcemia. Surgical resection is curative in most cases and long-term prognosis is excellent. Hypertension rarely persists after removal of the tumor, but remained in one of our two patients.

Congenital mesoblastic nephroma presenting with massive hematuria and hemorrhagic shock: report of one case

Congenital mesoblastic nephroma (CMN) is a rare benign tumor that occurs during the neonatal period and early infancy. The vast majority of these tumors present as asymptomatic palpable abdominal masses. We describe an unusual presentation of a CMN in a 10-month-old male infant who presented with massive hematuria and the development of hemorrhagic shock. Abdominal ultrasound showed a heterogeneous solid complex mass measuring 4.8 x 3.5 cm arising from the upper pole of the left kidney. The patient was resuscitated using intravenous fluids and blood transfusions because persistent massive bloody urine leading to progressive shock occurred the night of the admission day. Preoperative diagnosis was possible Wilms tumor of the left kidney. The histopathological findings were consistent with the character of a cellular variant of CMN. The patient was free of recurrence and metastasis at the 2-year follow-up examination. Our case report suggests that CMN is a rare benign renal tumor during infancy and may present with unusual massive hematuria and shock.

THE OUTCOME OF PRENATALLY DIAGNOSED RENAL TUMORS

PURPOSE

We assessed the incidence of perinatal morbidity and evaluated the outcome in children with prenatally diagnosed renal tumors in a retrospective multicenter study.

MATERIALS AND METHODS

A review of the records of patients from 20 institutions identified 28 children with prenatally diagnosed renal tumors. Prenatal findings, clinical charts, and radiological, surgical and pathological reports were reviewed in this study.

RESULTS

There were 26 congenital mesoblastic nephromas and 2 Wilms tumors. One or more complications were identified in 20 of the 28 cases (71%) during the perinatal period. Polyhydramnios was observed in 11 fetuses (39%), 2 presented with hydrops fetalis and 7 presented in acute fetal distress requiring emergency cesarean section, of which 1 died in utero before delivery. Median gestational age of the 27 neonates born alive was 35 weeks (range 29 to 39), including 13 (46%) who were pre-term (less than 34 weeks of gestation). Complications at birth included hemodynamic instability in 3 newborns, of whom 2 underwent emergency surgery, respiratory distress syndrome in 8 (30%) and hypertension in 6 (22%). Surgical complications occurred in 7 patients (26%), including tumor rupture in 1 and intraoperative bleeding with postoperative death in 1. At a median followup of 42 months (range 2 to 105) 26 of the 27 children were in complete remission.

CONCLUSIONS

Fetal renal tumors have an excellent oncological outcome but a high risk of perinatal complications. Prenatal diagnosis should allow planning the delivery at a pediatric tertiary care center to avoid a potentially life threatening condition in neonates in the first hours of life.

Prenatal diagnosis of congenital mesoblastic nephroma associated with renal hypertension in a premature child

In the present article, we report, for the first time, a prenatal diagnosis of a congenital mesoblastic nephroma in combination with a post-partum hyperreninemia with hypertension. A newborn was delivered at 35 weeks gestation who had an intrauterine diagnosis of a renal mass as early as 32 weeks gestational age by ultrasound examination. Tumor nephrectomy was performed on day 11 after delivery when an increase in hypertension was observed in the newborn.

Cellular congenital mesoblastic nephroma with contralateral medullary nephrocalcinosis

Congenital mesoblastic nephroma is the most common renal mass in the newborn period and can present with atypical findings. Certain associated conditions such as hypercalcaemia, hypertension and reninism have been described. We report a cellular variant of congenital mesoblastic nephroma with hypercalcaemia and contralateral medullary nephrocalcinosis.

Renal tumors in infants less than 6 months of age

BACKGROUND/PURPOSE

Renal tumors are rare in infants less than 6 months of age and may have associated paraneoplastic symptoms. To better define the characteristics of these tumors the authors reviewed their 10-year institutional experience.

METHODS

The authors searched the pathology database to identify all renal tumors resected at their institution since 1992 (after IRB approval and guidelines). The clinical presentation, operative details, pathology, and outcome for all children < or = 6 months of age were reviewed.

RESULTS

Of 101 children who had renal tumors resected during this period, 11 (11 %) were 6 months of age or less. Histopathologic examination showed congenital mesoblastic nephroma (CMN) in 7 patients (4 with cellular features), Wilms' tumor in 3 patients, and ossifying renal tumor of infancy in 1. Renal masses were detected antenatally in 2 patients and during newborn examination in 1 patient; however, the mean age at diagnosis was 72 +/- 18 days. Ten children had a palpable abdominal mass, 3 had gross hematuria, and 6 had hypertension (4 CMN; 2 Wilms'). Only 1 child had hypercalcemia (cellular CMN). Ten infants had nephroureterectomy, and 1 had a partial nephrectomy. All patients had either stage I or II disease. At follow-up (mean 4.2 +/- 1.2 years) 10 patients are alive with no evidence of disease. One newborn with hydrops and a very large congenital Wilms' tumor had abdominal compartment syndrome and died during surgery.

CONCLUSIONS

About 10% of renal masses may occur in infants less than 6 months of age. Although mesoblastic nephroma is the most common renal tumor in this age group, Wilms' tumor also may be seen. Paraneoplastic syndromes, such as hypertension and hypercalcemia, are common in these infants and are not specific for tumor type. These tumors generally present at an early stage and have an excellent prognosis overall.

[Congenital mesoblastic nephroma with multiple cysts]

Mesoblastic nephroma is a rare, benign congenital disease with a clinical presentation similar to that of Wilms tumour. It was described for the first time by BOLANDE in 1967. The authors report the case of a 6-month-old infant admitted for investigation of an abdominal mass. The radiological assessment (ultrasonography. CT) concluded on a right intrarenal retroperitoneal tumour occupying almost all of the abdominal cavity, predominantly cystic suggesting a diagnosis of non-metastatic Wilms tumour. Radical ureteronephrectomy was performed. The outcome was favourable with a follow-up of 2 years. Histological examination corrected the diagnosis to mesoblastic nephroma by showing a fibrous tumour composed of spindle cells resembling muscle cells, associated with intracystic haemorrhage. The authors emphasize the clinical and radiological features of this tumour, its treatment (exclusively surgical) and its good prognosis (98% survival).

Prenatal diagnosis of congenital mesoblastic nephroma in mid-second trimester by sonography and magnetic resonance imaging

Although congenital mesoblastic nephroma (CMN) is a rare benign congenital renal tumor, it is the most common solid renal tumor in the newborn period. The most common presentation of congenital mesoblastic nephroma is polyhydramnios, and only one case with prenatal fetal hydrops has been previously reported. Prenatal diagnosis of CMN has previously been made on the basis of the findings of sonography in the third trimester, and magnetic resonance imaging (MRI)-based diagnosis has been reported recently. Here we report a case of prenatally diagnosed classical type CMN diagnosed at 22 + 3 weeks of gestation based on the findings of sonography and magnetic resonance imaging. The characteristic imaging findings in this case were fetal hydrops and polyhydramnios. To our knowledge, this is the youngest reported gestational age for prenatal diagnosis of CMN and it is the second case of CMN associated with fetal hydrops detected prenatally.

Congenital mesoblastic nephroma associated with polyhydramnios and hypercalcemia

Congenital mesoblastic nephroma (CMN) can present with atypical clinical and imaging findings. A premature male neonate was born to an 18-year-old woman after 33 weeks' gestation, which was complicated by polyhydramnios and placenta abruptio. A right abdominal mass was diagnosed antenatally. From the 1st day of life, the newborn had hypercalcemia with initially normal parathormone levels and polyuria for the first hours of life and normal urine output afterwards. Ultrasonographic study and magnetic resonance imaging of the abdomen showed at the upper pole of the right kidney a heterogeneous, solid, poorly defined mass, partially surrounded by a subcapsular fluid collection mimicking malignant rhabdoid tumor of the kidney. Surgical resection revealed a CMN of mixed, classic, and in areas, cellular type. One year after the resection, the patient is asymptomatic and normocalcemic. In conclusion, CMN may present with atypical clinical and imaging findings, necessitating an extensive work-up in order to exclude highly malignant renal tumors of the neonatal period.

Cytogenetic and molecular characterization of a congenital mesoblastic nephroma

A newborn baby boy was diagnosed with the mixed form of congenital mesoblastic nephroma (CMN) representing both classic and cellular histology features in the renal tumor. Additionally, the patient had skin and bone lesions consistent with multifocal involvement of a generalized infantile fibromatosis (IFS). Both skin and bone lesions were distinctly different from CMN and did not represent metastasis. The primary tumor cell line (MCH-MN-1), established from the resected right kidney tumor, had a diploid DNA content. Cytogenetic studies revealed deletion on the long arm of chromosome 3 (q21q24) and duplication on the short arm of chromosome 11 (p15). MCH-MN-1 cells expressed ETV6-NTRK3 gene fusion transcripts, characteristic of cellular and mixed forms of CMNs. The cells had high p21 and low Bax mRNA expression in the reverse transcriptase-polymerase chain reaction (RT-PCR) assay. The high level of proliferative marker (Ki67) mRNA expression correlated well with the pluripotent nature of MCH-MN-1 in tissue culture (cell doubling time = 12.4 h). Our results showed that MCH-MN-1 might be a good model cell line for investigations on mesoblastic nephroma.

The presence of hydrops fetalis in a fetus with congenital mesoblastic nephroma

We report the first prenatal diagnosis of a case of congenital mesoblastic nephroma complicated by hydrops fetalis. Congenital mesoblastic nephroma is generally thought to be a benign disease but when complicated by hydrops fetalis it may be a potentially lethal condition.

Polyhydramnios and hypercalcemia associated with congenital mesoblastic nephroma: case report and a new appraisal

BACKGROUND

Polyhydramnios and hypercalcemia are known complications of congenital mesoblastic nephroma. Hypercalcemia has been shown to cause polyuria. Polyuria is believed to be the probable cause for the polyhydramnios, but the exact mechanism remains unknown. To our knowledge, this is the first reported case of a relationship between hypercalcemia and polyhydramnios.

CASE

A 26-year-old primigravida was diagnosed with congenital mesoblastic nephroma and polyhydramnios at 36 weeks' gestation. Neonatal hypercalcemia was detected immediately after delivery at 40 weeks' gestation. After removal of the nephroma, the calcium level normalized.

CONCLUSION

Hypercalcemia may be the mechanism underlying polyhydramnios in cases of congenital mesoblastic nephroma. Calcium levels should be monitored after delivery, and prompt surgical removal of the tumor should be performed.

Presence or absence of trisomy 11 is correlated with histologic subtype in congenital mesoblastic nephroma

Fluorescence in situ hybridization utilizing a probe for the alpha satellite repeat sequence on chromosome 11 was used to detect variations in the number of chromosomes 11 in 24 formalin-fixed, paraffin-embedded congenital mesoblastic nephromas. Evidence of trisomy 11 was found in nearly half of the tumors. More importantly, the presence of trisomy 11 was associated with the cellular histologic variant of this tumor.

[An atypical multilocular cystic nephroma presenting recurrent lumbago]

A 54-year-old female suffered from repeated flank pain. A large, irregular cystic mass that compressed and distorted the left pelviocalyceal system was found. She underwent left nephrectomy. The cyst arose from the inner zone of the kidney. Although monolocular grossly, it was compatible with the multilocular cystic nephroma on the microscopic examination.